1. Field of the Invention
The invention relates to a method and device for video signal enhancement, and to a display apparatus comprising such a video signal enhancement device.
2. Description of the Related Art
U.S. Pat. No. 5,734,746 discloses a picture signal enhancement circuit having a circuit for measuring a histogram of a picture signal, and a non-linear processing circuit for enhancing the picture signal in dependence upon the measured histogram.
U.S. Pat. No. 5,848,181 discloses an image processing apparatus for correctly extracting a uniform region having a small luminance level change from a noise-containing image. To this end, the image processing apparatus includes a differentiator for extracting a high frequency component of a luminous signal of the image within one screen, a histogram generating module for generating a histogram of the output value of the differentiator, a coefficient calculating module for analyzing the histogram to calculate a predetermined coefficient indicative of likeliness of the uniform region, and a pixel-position-depending coefficient producing module for establishing a correspondence relationship between the predetermined coefficient calculated by the coefficient calculating module and all of the pixel positions in the image in correspondence to the luminous level of the luminance signal from each of the pixel positions. The thus formed uniform region detecting apparatus is used in an edge enhancing apparatus in which an output of a uniform region detecting apparatus is applied to an edge enhancer that also receives the luminous signal. So, this prior art apparatus uses histogram detection only in uniform region detection.
It is, inter alia, an object of the invention to provide an improved video signal enhancement. To this end, the invention provides a method of enhancing a video signal.
In a video signal enhancement in accordance with the present invention, a video signal is histogram-based processed to obtain a histogram-processed video signal, and a sharpness of the histogram-processed video signal is enhanced to obtain an output video signal in dependence upon a sharpness enhancement control signal derived from at least the histogram-processed video signal. Advantageously, the sharpness enhancement control signal represents a derivative of the histogram-processed video signal.
These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.